The present invention relates to an exhaust aftertreatment device for aftertreatment of exhaust gas of an internal combustion engine.
The following discussion of related art is provided to assist the reader in understanding the advantages of the invention, and is not to be construed as an admission that this related art is prior art to this invention.
An exhaust aftertreatment device is provided to perform an aftertreatment procedure for exhaust gases produced by the internal combustion engine. As such, an exhaust aftertreatment device may also be referred to as emission control device. Exhaust produced by the internal combustion engine is fed to the exhaust aftertreatment device and flows there through. Exhaust is then released downstream of the exhaust aftertreatment device into the atmosphere for example.
The exhaust aftertreatment device includes an SCR catalyst by which a selective catalytic reduction of pollutants contained in the exhaust gas is executed. During selective catalytic reduction, in particular nitrogen oxides, also referred to as NOx, e.g. nitrogen oxide (NO) or nitrogen dioxide (NO2), are reduced. A reductant or reducing agent is hereby used to carry out the selective catalytic reduction. An example of a reductant includes ammonia (NH3). However, since ammonia is difficult to handle, it is normally produced only in the exhaust aftertreatment device, in particular through thermolysis. For this purpose, the reductant in the form of a liquid urea is initially added by a reductant feeding device, situated upstream of the SCR catalyst, at an entry point into the stream of exhaust gas. The reductant mixes with the exhaust gas from the entry point onwards in downstream direction and flows together with the exhaust gas in the direction of the SCR catalyst and through it. The better the mixture or intermingling of reductant with the exhaust gas before entering the SCR catalyst, the more efficient the SCR catalyst operates. For that reason, it has been proposed to arrange a mixing device in flow direction between the entry point and the SCR catalyst in an attempt to provide a mixing of the reductant with the exhaust gas. The results were unsatisfactory however.
It would be desirable and advantageous to provide an improved exhaust aftertreatment device to obviate prior art shortcomings.